1. Field of the Invention
The present invention relates, generally, to an apparatus for freezing liquid food products. More particularly, the invention relates to an apparatus for freezing liquids in a continuous flat slab and subsequently cutting the slab into discrete pieces.
2. Description of the Prior Art
Although the prior art includes various devices and methods for freezing materials, particularly liquids, these devices and methods are believed to have significant limitations and shortcomings. U.S. Pat. No. 2,282,525 to Maguire, for instance, discloses an apparatus for freezing liquid on a belt but there are no side constraints for the liquid. The apparatus is primarily intended to freeze cream, which presumably is sufficiently viscous and solidifies sufficiently fast so that side constraints are not required. It would not work well for less viscous liquids since those liquids would run off the conveyor before freezing.
For freezing other liquids, stationary side constraints, or dams, cannot be used directly against the liquid moving on the conveyor because, as the liquid freezes, it would adhere to the stationary dams. U.S. Pat. No. 3,280,590 to Larsson and U.S. Pat. No. 3,253,420 to De George disclose vertically oriented side belts traveling with the main conveyor to constrain liquid, primarily coffee extract, as it freezes. De George also uses a thin film of ice as a separate layer between the freezing belt and coffee extract.
Another expedient recognized in the prior art is the use of side belts. Side belts, however, add complexity to the freezing apparatus and must be well fitted and synchronized with the main conveyor belt. Furthermore, significant product may remain attached to the side belts at the discharge end and be lost.
As an alternative to side belts, side skirts have been bonded to the continuous main conveyor belt to provide a continuous trough for the liquid. However, use of such side skirts has been troublesome. Product tends to stick to the side skirts upon freezing, even with the use of release coatings, and a significant portion remains with the side skirts at the discharge end, thereby contributing to significant loss. Such product must be cleaned and removed from the continuous belt before the belt returns to the beginning of the freezing line. Furthermore, since the liquid expands upon freezing, significant pressure is exerted against the side skirts which may break the bond or tear the side skirt. U.S. Pat. No. 3,606,763 to Bevins addresses this problem by providing rotating scraper wheels along the side skirts to remove semi-solid coffee extract to keep it from freezing and adhering to the side skirts. This requires optimal placement of the scraper wheels at the point where the liquid becomes a semi solid, which depends on the material and freezing cycle used. Slight variations in the freezing cycle or line speed may require repositioning of the wheels. Other liquids may not exhibit a significant semi-solid state during freezing which is required for the apparatus to work.
All of the freezing systems discussed use continuous belts made of material such as stainless-steel as the main conveyor belt. Though a continuous belt offers the advantage of being reusable, when liquids freeze to it and are removed, a thin film of frozen liquid often remains on the belt. This film can grow during subsequent freezing operations and eventually may cause significant problems when separating the belt from the mass of frozen material. Ideally the belt should be cleaned upon its return and prepared for the next freezing cycle, however, the extra steps and apparatus add cost and complexity to the freezing operation.
The present invention provides an improved liquid freezing and cutting apparatus which overcomes the limitations and shortcomings of the prior art.
The present invention provides an apparatus for freezing and cutting liquids in a continuous process. One portion of the apparatus produces a continuous moving slab of frozen material, and another portion of the apparatus cuts the moving slab into discrete pieces.
The freezing portion of the apparatus includes a freezing table using a transfer film or belt for transporting liquid to be frozen across the top surface thereof. Spaced parallel side dams are attached to the freezing table and extend upwardly beyond the top surface thereof, preferably generally vertically. The side dams are spaced at a distance less than the width of the film or belt to allow the lateral edge surface thereof to extend upwardly against the adjacent side dams to form a trough. A front dam spans the side dams near the liquid input end of the table to constrain the liquid dispensed nearby, the dam being provided with sufficient clearance between its bottom surface or edge and the top of the freezing table to allow passage of the film thereunder, yet prevent seepage or escape of liquid. The front dam has film guide slots which receive the edges of the film to aid in the initial folding of the edge surfaces of the film against the side dams. A screed is provided across the side dams for controlling the thickness of liquid on the film downstream of the screed. In the preferred embodiment the film is a noncontinuous film, preferably polyethylene, that is unwound from a storage roll at the input end of the freezing table and wound onto a take-up roll at the discharge end of the table. In the alternative, a continuous belt may be adapted for use in the system.
The cutting portion of the apparatus is located near the discharge end of the freezing table and includes a plurality of transversely spaced cutting devices for cutting the frozen liquid into longitudinal strips, and a device for cutting the longitudinal strips into discrete pieces. In the preferred embodiment, the transverse cutting devices are circular saw blades disposed in parallel arrangement in two counter-rotating rows, and a guillotine cutter is used downstream of the saw blades to cut the strips into portions.
The features, benefits and objects of this invention will become clear to those skilled in the art by reference to the following description, claims and drawings.